1. Field of the Invention
The present invention relates to a display apparatus and, in particular, to an image display apparatus using an image display panel with a storage means built inside for each pixel, in which the structure of the storage means is simplified, the reduction of an aperture ratio is prevented, and low power consumption is achieved. The present invention further relates to an image display module using the image display apparatus.
2. Background Art
Thin and light image display apparatuses employing various image display panels such as liquid crystal display panels, plasma display panels, or organic electroluminescence (EL) panels, are known. In the field of image display panels constituting the image display apparatus of this type, the so-called active matrix image display apparatuses are the mainstream. The active matrix image display apparatus comprises many pixels arranged in a matrix and are provided with active elements to control the on/off states of each pixel. Thin film transistors or thin film diodes are widely used as the active elements used in image display apparatuses.
Although image display apparatuses using liquid crystal display panels having thin film transistors as active elements are described hereinafter as examples of the image display panel, it is needless to say that the present invention is also applicable to other types of image display panels and to image display apparatuses using those panels. One pixel corresponds to each pixel in a monochrome display. In the case of color display, one color pixel means a unit pixel (sub-pixel) responsible for each color. However, unless particularly necessary, a unit pixel for one color pixel is described hereinafter just as a “pixel.”
An example of the above active matrix image display apparatuses is known (see JP Patent Publication (Kokai) No. 8-194205 A 1996, for example). The example is provided with the so-called static semiconductor storage means (hereinafter referred to as “image memory element” or simply “memory element”) for each pixel to control active elements such as thin film transistors or thin film diodes used for the on/off states of pixels, so as to reduce power consumption. JP Patent Publication (Kokai) No. 2001-306038 discloses a liquid crystal display apparatus capable of reducing power consumption. The liquid crystal display apparatus comprises a data retention means for retaining image data supplied to a plurality of pixels. A voltage is applied to the liquid crystal based on the image data retained in the data retention means. A dynamic semiconductor memory element is used for the data retention means of the LCD apparatus disclosed in the latter publication above.
However, the image memory element provided for each pixel of the image display panel constituting the conventional image display apparatus as described above is configured using semiconductor elements, or semiconductor elements and capacitors. Therefore, it requires a large number of semiconductor elements to be built into a pixel area, or a large area for accommodating capacitors. In other words, the conventional image display apparatus comprising static image memory elements requires a large number of transistors, making it difficult to manufacture the image display panel and also reducing the effective display area in the pixel region, or the aperture ratio.
Further, in the case of the image display apparatus with dynamic image memory elements, a capacitor is used to store information, so that an area is required for forming the capacitor in the pixel region. Thus, the effective area in the pixel becomes small, resulting in a reduced aperture ratio. Furthermore, in the dynamic image memory elements, the charge stored in the capacitor in accordance with stored image data decreases with time. Accordingly, periodic refreshing must be carried out to prevent changes in the stored image data. As a result, circuit configurations inside and outside the pixel become complicated, and the circuit size becomes large due to the requirement for the refreshing circuit.
In addition, since an image memory element disclosed in the above prior art is a volatile memory, in which image data disappears when the power is turned off, constant voltage application to the image memory element or data-rewriting when the power is turned on is required, which is one of the obstacles to reducing power consumption.
As described above, there have been many problems to be solved concerning image display apparatuses using conventional image display panels. A first object of the present invention is to provide an image display apparatus comprising an image display panel, which simplifies the configuration of an image memory element provided for each pixel of the image display panel to prevent the reduction of the pixel aperture ratio, and achieves low power consumption by having a configuration allowing image data to be retained inside the pixel when the power is off.
A second object of the present invention is to provide a low power consumption image display module using the above image display apparatus.
In order to achieve the above first object, according to the present invention, an image display apparatus comprises:
an image display panel having a display element comprising a plurality of pixels arranged in a matrix at crossing points where a plurality of scanning electrode lines cross a plurality of signal (display data) electrode lines;
a scanning electrode line selection circuit for selecting the scanning electrode lines of the image display panel;
a signal electrode line drive circuit for driving the signal electrode line; and
storage means for storing display data for each pixel.
The storage means comprises a resistor connected to each pixel and the display data is stored in the pixel by way of the resistance value of the resistor.
The storage means (hereinafter also referred to as “image memory element”) is preferably controlled by a current signal, and furthermore, it may be nonvolatile. The image memory element uses resistance changes caused by phase changes or phase transition of a recording medium constituting the image memory element. As the phase change medium, a material that exhibits resistance due to phase changes between a crystal state and an amorphous state can be used, and a GeSbTe phase change medium is preferably used. The pixels connected to the image memory element may be electrically isolated from the scanning and the signal electrode lines. In such a case, as with the passive matrix type, rewriting means always electrically connected to the scanning and signal lines can be driven directly by the scanning and the signal electrode lines.
Further, reading means for reading data stored in the storage means may be provided. An operating means for comparing the image data (referred to as display data or display signal) read by the reading means with display data to be subsequently displayed is provided, and the read image data is thereby compared with the subsequent image data. Then, the stored data in the storage means is rewritten only when they are different. Further, a plurality of storage means can be provide in one pixel.
In order to achieve the second object, according to the present invention, the image display module comprises:
an image display panel having a display element comprising a plurality of pixels arranged in a matrix at crossing points where a plurality of scanning electrode lines cross a plurality of signal electrode lines;
a recording apparatus for recording display data in the image display panel; and
a display drive apparatus for displaying the display data recorded in the image display panel by the recording apparatus,
wherein the image display panel can be connected to one or both of the recording apparatus and the display drive apparatus.
The image display panel comprises a nonvolatile storage means for storing the display data for each pixel, a scanning line connection portion for inputting a scanning signal into the scanning line, a signal line connection portion for inputting a display data signal into the signal line, a drive line connection portion for inputting a drive signal for driving the pixel, and a power line connection portion.
In addition, the recording apparatus comprises a scanning line selection circuit, a signal line drive circuit for driving the scanning and signal lines of the liquid crystal display apparatus, a signal control circuit, and a recording apparatus connection portion for connection to the signal line connection portion and the drive line connection portion.
The recording apparatus is connected to the image display panel via the recording apparatus connection portion and the data stored in the storage means is rewritten by inputting a rewriting signal of the storage means into the scanning line and signal line connection portions.
The display drive apparatus comprises an opposite electrode drive circuit, a power circuit, and a display drive apparatus connection portion for connection to the drive line connection portion and the power line connection portion of the image display panel and the display drive apparatus is connected to the image display panel via the display drive apparatus connection portion to display the display data stored in the image display panel.
Further, each pixel of the image display panel has a plurality of image memory elements and a plurality of images are changed and displayed by switching these image memory elements.
The present invention is not limited to the above configurations and configurations of embodiments described below, and it is needless to say that various modifications are possible without deviating from the technical idea of the present invention.
This specification includes part or all of the contents as disclosed in the specification and/or drawings of Japanese Patent Application No. 2002-232317, which is a priority document of the present application.